MEASUREMENT OF ACCURATE HEAT-CAPACITIES BY DIFFERENTIAL SCANNING CALORIMETRY COMPARISON OF DSC RESULTS ON PYRITE (100-K TO 800-K) WITH LITERATURE VALUES FROM PRECISION ADIABATIC CALORIMETRY

The heat capacity of a sample of FeS2, pyrite, has been measured from 100 to 800 K by differential scanning calorimetry (d.s.c.) as a test of the accuracy of the apparatus and methods employed. The heat capacity of the pyrite sample had previously been determined in another laboratory by precision adiabatic calorimetry; therefore, excellent literature values were available for comparison with the present results. The apparatus used was the Perkin-Elmer DSC-2, augmented by the Tektronix calculator and digital interface available from Perkin-Elmer. Two runs on pyrite were performed, using different measuring techniques. Calculator programs for these techniques are described. By either method the accuracy of the pyrite heat-capacity measurements was approximately 1 per cent over most of the temperature range, and generally within 2 per cent at the very lowest and highest temperatures. Results are presented which show that the use of liquid-nitrogen coolant with helium exchange gas in the DSC-2 is an unfavorable combination, producing distorted peak shapes for transitions. Neon is recommended as the exchange gas when liquid-nitrogen temperatures are necessary. Significant improvements in the peak shapes are then observed. © 1979.